BMJ  2004;328:E270-E271 (28 February), doi:10.1136/bmj.328.7438.E270

BMJ USA: Editorial

Automated defibrillators

Best seen as part of CPR

Three articles published in this issue (pp 23, 28, 45) nicely delineate several key issues related to use of automated external defibrillators (AEDs). These articles not only place the relative effectiveness of AEDs into better context, but they also provide insight into the limitations of AEDs and starting points for further research.

AEDs have been highly effective in certain public settings where designated rescuers (eg, flight attendants or security guards) or a large number of bystanders are immediately available.^1-3 AED use within first two minutes after collapse can dramatically improve outcome over traditional methods.

In the most successful traditional emergency medical services (EMS) systems, overall rates of hospital admission following sudden out-of-hospital cardiac arrest associated with ventricular fibrillation (VF) exceeded 60%⁴ when bystanders witnessed the event and performed basic cardiopulmonary resuscitation (CPR). This is a near-miraculous statistic considering that VF is typically unexpected, unheralded, and almost uniformly lethal if CPR or defibrillation is not performed within the first few minutes.^4,5

Nevertheless, even in such successful systems where the community knew and performed CPR in nearly 50% of cases, the majority of resuscitated patients still arrived at the hospital unconscious. In turn, only two thirds of these patients eventually awoke and survived with good neurological status. Moreover, when bystanders did not perform CPR, near-equal numbers of admissions occurred, but many fewer awoke and survived.⁴

AEDs have helped to improve those results. In a recent study of public use of AEDs at the Chicago airports, there was not only an extremely high resuscitation rate, but all of the resuscitated patients regained normal neurological status.³ In fact, the majority of survivors were awakening before EMS crews arrived, and almost all by hospital admission. This obviated the need for traditional intensive care unit (ICU) monitoring, mechanical ventilation, and other expensive therapies. Arguably, this increase in number of functional survivors might lead to additional health care costs (eg, placement of implantable defibrillators, cardiac surgery, coronary artery interventions), but this is a more desirable use of resources than avoidable and unfruitful ICU costs.

However, despite well-deserved enthusiasm for AEDs, most cardiac arrests do not occur in public settings in view of multiple witnesses.⁵ The "successful" (high survival) reports about AEDs typically come from unique, targeted circumstances such as casinos, airplanes, and airports providing a high concentration of AEDs, intensive publicity, and many potential rescuers on site.^1-3 As Liddle and colleagues state in this issue, AED use is optimal in the first 90 seconds. That time criterion generally limits success to circumstances predisposing to immediate recognition of a cardiac arrest by a bystander, along with immediate access to a highly visible AED. In the very first AED case reported from Chicago's O'Hare International Airport, the collapse occurred in front of one of the authors (SCV), yet the time from collapse to shock still exceeded 90 seconds. Even under optimal circumstances such as this, it takes time to recognize the collapse, access the AED, expose the chest, apply the pads, perform final assessments, and start the device.³ Therefore, a "zero response interval" is not a zero interval to shock. All survivors in that study received shocks within five minutes and all received immediate performance of basic CPR techniques, even if briefly.

By contrast, in their clinical trial of first-responder AED use, van Alem and colleagues reported "collapse to shock" intervals, demonstrating that even with first-responders, shocks were not given for over 11 minutes. This information is critically pertinent because evolving evidence demonstrates that countershocks provided to a relatively ischemic heart may be detrimental.⁶ Controlled trials in systems with dispatch to scene arrival intervals of about 5 minutes (perhaps translating into a collapse to shock interval of 8 minutes or more) demonstrate that survival with good neurological recovery is improved if basic CPR is first provided for a few minutes prior to the first shock.^6-8 Therefore, in addition to a potential type II statistical problem (not enough numbers to detect a difference in survival) and the discussed improvements in the dispatch process, it is quite possible that this study might have shown improved survival rates with alternative strategies for the timing of CPR and AED use.

Also in this issue, Walker and colleagues raise further concern that widespread placement of AEDs in public locations (where only 10-15% of sudden deaths occur) may not be cost-effective. Again, these costs might be even higher if one survives to undergo subsequent surgeries and procedures. At the same time, the reported survival rates are much lower than most other public AED outcome studies.^1-3 This may also reflect relative delays in AED use or other variables confounding their successful use such as overzealous ventilation during resuscitation or lack of basic CPR prior to shocks if there was a delay in accessing the defibrillator.^6,9

They may also reflect less aggressive public awareness campaigns and perhaps a public focus on the device alone. If there is one central "take-home lesson," it is that AEDs are best seen as a component of CPR training and performance. While they clearly can make CPR more effective, AEDs are just a part of CPR. In turn, all of us potential bystanders need to learn CPR—including AED use—for the sake of our family, our friends, and costs to our health care system.

University of Texas Southwestern Medical Center and the Parkland Health and Hospital System, Dallas Metropolitan Medical Response System for Anti-Terrorism and the Dallas Metropolitan BioTel (EMS) System Dallas, TX Paul.Pepe{at}UTSouthwestern.edu

Public Safety Solutions, Inc, Chicago, IL, Chicago HeartSave Program SHERORD{at}aol.com

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Papers pp 23, 28

Clinical review p 45

Competing interests: PEP's institution has received support from multiple defibrillator companies to support educational events.

References

1. Valenzuela TD, Roe DJ, Nichol G, Clark LL, Spaite DW, Hardman RG. Outcomes of rapid defibrillation by security officers after cardiac arrest in casinos. N Engl J Med 2000;343: 1206-1209.[Abstract/Free Full Text]
2. Page RL, Joglar JA, Kowal RC, Zagrodzky JD, Nelson LL, Ramaswamy K, et al. Use of automated external defibrillators by a U.S. airline. N Engl J Med 2000;43: 1210-1216.
3. Caffrey SL, Willoughby PJ, Pepe PE, Becker LB. Public use of automated external defibrillators. N Engl J Med 2002;347: 1242-1247.[Abstract/Free Full Text]
4. Eisenberg M, Bergner L, Hallstrom A. Paramedic programs and out-of-hospital cardiac arrest: I. Factors associated with successful resuscitation. Am J Public Health 1979;69: 30-38.[Abstract/Free Full Text]
5. Cummins R, Ornato J, Thies W, Pepe P. Improving survival from sudden cardiac arrest: the "chain of survival" concept. A statement for health professionals from the Advanced Cardiac Life Support Subcommittee and the Emergency Cardiac Care Committee, American Heart Association. Circulation. 1991;83: 1832-1847.[Free Full Text]
6. Pepe PE, Fowler R, Roppolo L, Wigginton J. Re-appraising the concept of immediate defibrillatory attempts for out-of-hospital ventricular fibrillation. Crit Care (in press: January 2004).
7. Cobb LA, Fahrenbruch CE, Walsh TR, Copass MK, Olsufka M, Breskin M, et al. Influence of cardiopulmonary resuscitation prior to defibrillation in patients with out-of-hospital ventricular fibrillation. JAMA 1999;281: 1182-1188.[Abstract/Free Full Text]
8. Wik L, Hansen TB, Fylling F, Steen T, Vaagenes P, Auestad BH, et al. Delaying defibrillation to give basic cardiopulmonary resuscitation to patients with out-of-hospital ventricular fibrillation: a randomized trial. JAMA 2003;289: 1389-1395.[Abstract/Free Full Text]
9. Aufderheide T, Pirrallo R, Sigurdsson G, et al. Hyperventilation: a common and potentially life-threatening problem during cardiopulmonary resuscitation. Circulation 2003(suppl);108: 581 [abstract].

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